What are three physical properties often analyzed to identify covalent compounds?

Covalent compounds are compounds in which nonmetal atoms are bond and share electrons. 
In order to identify if a compound is covalent it must satisfy the following physical properties:
1. Covalent compounds generally have much lower melting and boiling points than ionic compounds.
2. Covalent compounds have soft or brittle solid forms.
3. Covalent compounds have poor electrical and thermal conductivity.

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Answer is to avoid experimental error